1. Technical Field
The present invention relates to a heat exchanger, and more particularly, to a heat exchanging condenser for use in an automative air-conditioning system.
2. Description of the Prior Art
With reference to FIG. 1, a conventional refrigerant circuit for use, for example, in an automotive air-conditioning system is shown. Circuit 1 includes compressor 10, condenser 20, receiver or accumulator 30, expansion device 40, and evaporator 50 serially connected through pipe members 60 which link the outlet of one component with the inlet of a successive component. The outlet of evaporator 50 is linked to the inlet of compressor 10 through pipe member 60 so as to complete the circuit. The links of pipe members 60 to each component of circuit 1 are made such that the circuit is hermetically sealed.
In operation of circuit 1, refrigerant gas is drawn from the outlet of evaporator 50 and flows through the inlet of compressor 10, and is compressed and discharged to condenser 20. The compressed refrigerant gas in condenser 20 radiates heat to an external fluid flowing through condenser 20, for example, atmospheric air, and condenses to the liquid state. The liquid refrigerant flows to receiver 30 and is accumulated therein. The refrigerant in receiver 30 flows to expansion device 40, for example, a thermostatic expansion valve, where the pressure of the liquid refrigerant is reduced. The reduced pressure liquid refrigerant flows through evaporator 50, and is vaporized by absorbing heat from a fluid flowing through the evaporator, for example, atmospheric air. The gaseous refrigerant then flows from evaporator 50 back to the inlet of compressor 10 for further compression and recirculation through circuit 1.
With further reference to FIGS. 1a, and 2-5, a prior art embodiment of condenser 20 as disclosed in Japanese Patent Application Publication No. 63-112065 is shown. Condenser 20 includes a plurality of adjacent, essentially flat tubes 21 having an oval cross-section and open ends which allow refrigerant fluid to flow therethrough. A plurality of corrugated fin units 22 are disposed between adjacent tubes 21. Circular header pipes 23 and 24 are disposed perpendicularly to flat tubes 21 and may have, for example, a clad construction. Each header pipe 23 and 24 includes outer tube 26 which may be made from aluminum and inner tube 28 made of a metal material which is brazed to the inner surface of outer tube 26. Outer tube 26 has slits 27 disposed therethrough. Flat tubes 21 are fixedly connected to header pipes 23 and 24 and are disposed in slits 27 such that the open ends of flat tubes 21 communicate with the hollow interior of header pipes 23 and 24. Inner tube 28 includes portions 28a which define openings corresponding to slits 27. Portions 28a are brazed to the inner ends of flat tubes 21 and ensure that tubes 21 are hermetically sealed within header pipes 23 and 24 when inserted in slits 27.
Header pipe 23 has an open top end and a closed bottom end. The open top end is sealed by inlet union joint 23a which is fixedly and hermetically connected thereto. Inlet union joint 23a is linked to the outlet of compressor 10. Partition wall 23b is fixedly disposed within first header pipe 23 at a location about midway along its length and divides header pipe 23 into upper cavity 231 and lower cavity 232 which is isolated from upper cavity 231. Second header pipe 24 has a closed top end and an open bottom end. The open bottom end is sealed by outlet union joint 24a fixedly and hermetically connected thereto. Outlet union joint 24a is linked to the inlet of receiver 30. Partition wall 24b is fixedly disposed within second header pipe 24 at a location approximately one-third of the way along the length of second header pipe 24 and divides second header pipe 24 into upper cavity 241 and lower cavity 242 which is isolated from upper cavity 241. The location of partition wall 24b is lower than the location of partition wall 23a.
In operation, compressed refrigerant gas from compressor 10 flows into upper cavity 231 of first header pipe 23 through inlet union joint 23a, and is distributed such that a portion of the gas flows through each of flat tubes 21 which are disposed above the location of partition wall 23b, and into an upper portion of upper cavity 241. Thereafter, the refrigerant in the upper portion of cavity 241 flows downward into a lower portion of upper cavity 241, and is distributed such that a portion flows through each of the plurality of flat tubes 21 disposed below the location of partition wall 23b and above the location of partition wall 24b, and into an upper portion of lower cavity 232 of first header pipe 23. The refrigerant in an upper portion of lower cavity 232 flows downwardly into a lower portion, and is again distributed such that a portion flows through each of the plurality of flat tubes 21 disposed below the location of partition wall 24b, and into lower cavity 242 of second header pipe 24. As the refrigerant gas sequentially flows through flat tubes 21, heat from the refrigerant gas is exchanged with the atmospheric air flowing through corrugated fin units 22 in the direction of arrow W as shown in FIG. 5. Since the refrigerant gas radiates heat to the outside air, it condenses to the liquid state as it travels through tubes 21. The condensed liquid refrigerant in cavity 242 flows out therefrom through outlet union joint 24a and into receiver 30 and the further elements of the circuit as discussed above.
With reference to FIG. 6 a portion of a similar prior art condenser which is disclosed in U.S. Pat. No. 4,825,941 is shown. Header pipe 13 includes slit 29 formed on an opposite side thereof from slits 27 and at a vertical location between two adjacent slits 27. Although not shown in the Figure, header pipe 13 could include a brazing layer 28 as shown in FIG. 4. Partition plate 70 includes smaller diameter semi-circular portion 70a and larger diameter semi-circular portion 70b integrally formed such that the two semi-circular portions are joined at their chordal surfaces. Portion 70a has a radius substantially equal to the inner radius of header pipe 13 and portion 70b has a radius substantially equal to the outer radius of header pipe 13. Partition plate 70 is disposed and soldered in slit 29 such that portion 70a fits flush against the inner surface of pipe 13 and the outer surface of portion 70b is disposed so as to be substantially even with the outer surface of header pipe 13. Both plate 70 and header pipe 13 are provided with layers of solder so as to ensure that no leakage of refrigerant fluid occurs between the interior portions of pipe 13 which are separated by plate 70, or from the interior of pipe 13 to the outside.
In the condenser shown in FIG. 6, header pipe 13 must be formed with a plurality of slits 29 and a corresponding plurality of partitions 70 having circular portions 70a and 70b, as described above. The process for constructing headers of this type is complicated and results in a great deal of wasted time and material if the parts do not fit or seal properly. Additionally, condensers are disposed at the high pressure side of a refrigeration circuit, and also may be mounted within the engine compartment in a position where they will be subjected to numerous highly concussive vibrations. As a consequence of the vibrations and the high pressure of the refrigerant in the condenser, undesirable leakage of the refrigerant through slits 29 to the atmosphere may occur. Therefore, lit is not desirable to increase the number of slits in header pipe 13 by the addition of slits 29 since this increase results in a corresponding increase in the possibility of refrigerant leaking to the outside of pipe 13.